Rotary line trimmers are in wide-spread use for trimming grass and other vegetation in areas not accessible by conventional lawn mowers. The line trimmers have a rotary head powered by a gasoline engine or an electric motor mounted on the end of an elongated boom. The rotary line trimmer head is typically mounted to a drive spindle which is pivotally mounted on the end of an elongated boom. Extending generally radially outward from the periphery of the line trimmer head, are one or more segments of line typically a 0.05 to 0.10 inch diameter monofilament line.
In use, when cutting portion of the line is damaged, it becomes necessary to replace the line. A number of varying mechanisms to achieve line replacement have been developed over the years. The most common technique is to include a spool of line within the head and incrementally advance the line extending a new segment to replace the damaged segment. This type of trimmer is typically the bump head variety in which the line incrementally advances in response to the trimmer head being bumped on the ground. There also exists trimmer head of the automatic variety in which the line incrementally advances in response to a significant change in rotational speed of the trimmer head, i.educing the engine to idle and then resuming full operational speed.
The problem associated with spool type trimmer heads is that the line may become tangled within the spool or welded to itself particularly in the instances of extended heavy use. Therefore, particularly in the commercial lawn services, there is a trend toward using trimmer heads which utilize fixed line segments which are simply discarded when worn and replaced with a new line segment. While this results in a smaller percentage of the line being actually used, the tangling problems are eliminated and heavier line gauges may be utilized. Heavier line gauges extend the interval of time between line replacements.
A variety of fixed line trimmer heads have been developed. Some utilize line segments which have an enlarged head formed thereon to retain the line to the trimmer head. Others use uniform cross-section segments of line that may be severed from a large spool. Uniform cross-section line enables the replacement line to be easily obtained from convenient low cost sources. Problems, however, occur in simply and securely attaching the uniform cross-section line segment to the trimmer head.